Two-photon polymerization of silica glass diffractive micro-optics with minimal lateral shrinkage.

Three-dimensional printing enables the fabrication of silica glass optics with complex structures. However, shrinkage remains a significant obstacle to high-precision 3D printing of glass optics. Here we 3D-printed Dammann gratings (DGs) with low lateral shrinkage (<4%) using a two-photon polymerization (2PP) technique. The process consists of two steps: patterning two-photon polymerizable glass slurry with a 515 nm femtosecond laser to form desired structures and debinding/sintering the structures into transparent and dense silica glass. The sintered structures exhibited distinct shrinkage rates in the lateral against longitudinal directions. As the aspect ratio of the structures increased, the lateral shrinkage decreased, while the longitudinal shrinkage increased. Specifically, the structure with an aspect ratio of approximately 60 achieved a minimal lateral shrinkage of 1.1%, the corresponding longitudinal shrinkage was 61.7%. The printed DGs with a surface roughness below 20 nm demonstrated good beam-shaping performance. The presented technique opens up possibilities for rapid prototyping of silica diffractive optical elements.

Stroke-like onset of calcified brain metastases with Wallerian degeneration: a case report and review of the literature.

INTRODUCTION: Metastatic brain tumors are a common complication of systemic cancer. They tend to have a chronic onset and are located at the gray-white junction of the cerebral hemispheres, those larger than 9.4 mm in diameter are often accompanied by substantial vasogenic edema. Herein, we report a rare case of calcified metastatic adenocarcinoma with Wallerian degeneration. In addition, we discuss the atypical manifestations of brain metastases. CASE REPORT: A 71-year-old man who went through stroke-like onset twice during 8 months with a history of resection of the left pulmonary adenocarcinoma 5 years prior was examined. Diffusion weighted magnetic resonance imaging of the brain showed an enlarged open-ring-shaped hyperintensity on the left periventricular white matter and basal ganglia, with Wallerian degeneration on the left cerebral peduncle. Brain computed tomography revealed nodular calcification of the lesion. The pathology of stereotactic biopsy indicated metastatic adenocarcinoma. CONCLUSION: When patients present with acute nervous system symptoms and a previous history of cancer, the possibility of metastases should be considered, even if neuroimaging is atypical.

Formation mechanism of bubbles in the crack healing process of fused silica using a CO2 laser.

The machining-induced cracks and other defects on the surface of fused silica would incur damage when irradiated by intense lasers, which greatly shortens the service life of the fused silica optical components. The high absorption coefficient of fused silica for far-infrared lasers makes it possible to use low-energy CO2 lasers to melt and heal micro defects on the surface, and hence improve its damage threshold under the service conditions of extremely intense laser. However, the air in the cracks may evolve into bubbles during the laser healing process, but the law of crack morphology evolution and the bubble formation mechanism have not been clearly revealed. In this work, a simulation model of the healing process of fused silica surface cracks under the effect of low-energy CO2 laser is established. Three bubble formation mechanisms (i.e., the uneven fluidity caused by temperature gradient, the collapse effect caused by inclined cracks, and the internal cracks) are identified based on the simulation results of cracks with various original morphologies and characteristic structural parameters. The simulated fused silica morphology is consistent with the results of the laser healing experiment. This work can provide theoretical guidance for the optimization of optical manufacturing parameters of fused silica, as well as the CO2 laser healing and polishing strategies.

Broadband absorption coating for large-curvature surfaces by atomic layer deposition.

For many applications, large curvature surfaces or complicated 3D structures are required to absorb light that falls on them to reduce stray light or energy collection. A novel, to the best of our knowledge, strategy with a metal-dielectric film stack by the atomic layer deposition technique is put forward to achieve broadband absorption coating covering both sides of a quartz tube completely. Absorptive metallic material of titanium-aluminum-carbon composite and dielectric material of aluminum oxide (Al2O3) is employed to realize high absorption (>99%) for the 400-780 nm band with the configuration of a six-layer metal-dielectric film stack. Good angle insensitivity up to 50° for P- and S-polarizations is demonstrated experimentally with the proposed structure on a glass slab. The average absorption of the coated quartz tube reaches as high as 99% for all curving areas on the inner and outer sides, while the nonuniformity is confined to 1.5% for the axial and circumferential directions. This presented approach has enormous potential in the fields of optical detection, optical imaging, optical sensing, and energy management.

Effect of laser pulse duration and fluence on DKDP crystal laser conditioning.

The impact of laser conditioning (LC) fluence and pulse duration on nanosecond (ns) laser damage performance of deuterated potassium dihydrogen phosphate (DKDP) crystal is studied. The result shows that higher LC fluence leads to a better damage resistance. In general, the sub-nanosecond LC effect is better than the nanosecond LC. However, in the range of 0.3 ns to 0.8 ns, the pulse duration has no obvious impact on the LC effect. An ultra-fast process characterization technology is employed to demonstrate that the cleaning effect of the protuberance defects on the surface is one of sub-ns LC mechanism. Eventually, a couple of optimized LC parameters that doubled the maximum damage threshold of DKDP crystal is proposed.

Orthotropic nystagmus in predicting the efficacy of treatment in posterior canal benign paroxysmal positional vertigo.

OBJECTIVE: To observe the type of nystagmus in each position of posterior semicircular canal benign paroxysmal positional vertigo (BPPV) after treatment with the Epley maneuver and analyze the relationship between the type of nystagmus in the second and third positions of the Epley maneuver and the effect of treatment. Then, the role of orthotropic nystagmus in predicting the success of posterior semicircular canal BPPV treatment was explored. METHODS: Two hundred seventy-six patients diagnosed with posterior semicircular canal BPPV who were admitted from September 2018 to October 2019 to Zhejiang Hospital were included. All patients were treated with BPPV diagnosis and treatment system (Epley maneuver). During the treatment, we observed and recorded the type of nystagmus in the second and third positions, including the direction and duration of nystagmus. One hour after the first treatment, all patients were evaluated by both the Dix-Hallpike and Roll tests to determine whether the treatment was successful. The difference in the success rate of treatment between different types of nystagmus was compared, and the differences in sensitivity and specificity of orthotropic nystagmus in the second and third positions in predicting the effect of treatment were compared. RESULTS: Among the 234 patients who had successful repositioning for the first time, the proportion of orthotropic nystagmus during the third position of the Epley maneuver was 88.9%, which was significantly higher than 23% in the unsuccessful group (42 cases) (P < 0.05) The proportion of patients with reversed nystagmus (4.7% vs 33.3%, P < 0.05) and no nystagmus (6.4% vs 42.9%, P < 0.05) was lower in the successful group than in the unsuccessful group. The proportion of orthotropic nystagmus during the second position of the Epley maneuver was 50.9%, which was also higher than the 19% in the unsuccessful group (P < 0.05). The proportion of reversed nystagmus (13.7% vs 31%, P < 0.05) was lower in the successful group than in the unsuccessful group. Additionally, the proportion of no nystagmus (35.5% vs 50%, P = 0.074) was lower in the successful group than in the unsuccessful group, but the difference was not statistically significant. The sensitivity of orthotropic nystagmus in the third position (88.9%) of the Epley maneuver in predicting the efficacy of treatment was higher than that of orthotropic nystagmus in the second position (50.9%), but there was no significant difference in specificity between the two. CONCLUSION: Orthotropic nystagmus during the Epley maneuver, especially in the third position, has certain value in predicting the efficacy of posterior semicircular canal BPPV repositioning, which is better than its predictive effect in the second position, whereas reversed nystagmus or no nystagmus in the third position is suggestive of unsuccessful repositioning. Therefore, clinicians can carry out individualized treatments based on nystagmus types during repositioning to improve the effect of treatment.

Broadband terahertz antireflective microstructures on quartz crystal surface by CO2 laser micro-processing.

Anti-reflection (AR) coating is a critical technology and an ongoing challenge for terahertz systems. The subwavelength structure (SWS) is an effective AR method, whereas the current manufacturing techniques, such as chemical etching and ultrafast laser processing, are low-efficient and low-quality for processing structures at the hundred-micron scale on hard brittle materials. We present a study of broadband SWSs directly ablated on the surface of quartz crystal by precisely controlled CO2 laser pulses, instead of commonly used ultra-fast lasers. The processing time of SWS can be shortened by two orders of magnitude compared with that by ultra-fast laser pulses. The SWS samples exhibit excellent AR properties with maximum transmittance of 97% at 0.71 THz, peak transmittance improvement of 13.5%, and optimal efficiency spectrum of 0.28-1.21 THz with transmittance >90%. The AR properties of SWS samples are in agreement with the simulated expectation and exist over a wide range of incidence angles up to ∼40°. The imaging of an object using SWS as the substrate shows an obvious improvement in imaging quality. We present an efficient and practical way to improve the transmission of optical components of materials, such as quartz crystal, alumina, and sapphire, in the terahertz band.

Determination of optimized removal functions for imprinting continuous phase plates using fuzzy theory.

A new evaluation method based on fuzzy theory was proposed to assess the manufacturing efficiency and accuracy of continuous phase plates (CPPs) with magnetorheological finishing imprinting. Two-dimensional sinusoidal waves were employed to verify the effectiveness of the proposed method theoretically and experimentally in terms of two parameters, error root mean square and processing time, which indicate the accuracy and efficiency of CPP manufacture. The weight factor was used for balancing the priorities of processing time and accuracy in our method. The simulations and experiments were compared based on our proposed method. The results show that the optimum removal functions for various spatial periods result in good agreement between simulations and experiments, and furthermore, relative errors are 6.07%, 2.62%, and 6.00% for CPPs with spatial periods of 12 mm, 18 mm, and 30 mm, respectively. All the results indicate that the method provides a valid and feasible way to select an optimized removal function for imprinting the patterns of CPPs.

Study of morphological feature and mechanism of potassium dihydrogen phosphate surface damage under a 351 nm nanosecond laser.

The surface damage morphology of potassium dihydrogen phosphate (KDP) crystal under 351 nm nanosecond laser irradiation is studied, and the formation mechanisms of each damage type are discussed. There are three unique types of KDP surface damage, namely, crack, shell, and crater, under the fluence between 5 and 15 J/cm2. The fracture feature of crack type damage indicates the pure mechanic process during laser exposure. Some cracks result in the upwarp of the material with a height of 0.1-0.5 µm. The shell is a most typical damage morphology with a proportion as large as about 80%. The transverse size of shell ranges from 5 to 82 µm, related to the fluence. The crater has a distinguished core structure related to the high-temperature process. The evidence of dehydration reaction is found in the core by energy dispersive spectrometer semiquantitative analysis. Internal morphology analysis with a focused ion beam suggests that the crack and shell damage originate from the surface or subsurface machining defects, while the crater damage is mainly due to material bulk defects.

A comparison of six clock-drawing test scoring methods in a nursing home.

BACKGROUND: Clock-drawing test (CDT) is widely used but lack of a suitable scoring method. AIMS: To compare the validity of six common CDT scoring methods and to find out the best one. METHODS: The drawing CDT was administered in a Chinese nursing-home inhabitants living on the mainland including 110 dementia, 118 MCI (mild cognitive impairment), and 133 random normal. We calculated the sensitivity and specificity of six scoring methods and applied the receiver-operating characteristic (ROC) curve statistic, including determining the area under the curve (AUC). RESULTS: (1) All six CDT scoring methods had a value of sensitivity higher than 80% and a specificity of 60% except Jouk and Tuokko. Freund got the highest sensitivity (92.73%) of that five for the testing of dementia and high sensitivity (82.20%) for MCI with an acceptable specificity (70.68%). (2) The AUC (area under the ROC curve) of all six CDT methods was over 0.8 for dementia, and for MCI, only Jouk and Tuokko were lower than 0.8. Mendez had the largest AUC of 0.872 for MCI, which closely followed by Freund with 0.859. (3) Freund predicted dementia best but had no significant difference (p > 0.05); it only had significant difference with Jouk and Tuokko (p < 0.001) and the method in MoCA (p < 0.05) for both MCI and cognitive impairment. CONCLUSIONS: Our study suggests that Freund scoring method could be the best one among the six evaluated scoring methods within our setting.

Ion beam planarization of diamond turned surfaces with various roughness profiles.

The effectiveness of ion beam planarization (IBP) to reduce surface roughness of diamond turned NiP surfaces was investigated. The surfaces with various spatial wavelengths and depths of turning marks were spray-coated and planarized with broad ion beam. The ion beam planarization was performed at a special angle where the etching rate of photoresist is closely similar to NiP. It is found that the combined process of spray-coating and ion-beam-planarization can effectively reduce the surface roughness of diamond turned NiP. The spatial wavelength and depth of turning marks have limited influence on surface roughness reduction rate. The final surface roughness after ion beam planarization is 30%~40% of the original roughness, irrespective of spatial wavelength and depth of turning marks. Extending planarization time does not alter surface quality after photoresist is etched away. These results show that the IBP is applicable to roughness minimization of diamond turned surfaces.

Post-processing of fused silica and its effects on damage resistance to nanosecond pulsed UV lasers.

HF-based (hydrofluoric acid) chemical etching has been a widely accepted technique to improve the laser damage performance of fused silica optics and ensure high-power UV laser systems at designed fluence. Etching processes such as acid concentration, composition, material removal amount, and etching state (etching with additional acoustic power or not) may have a great impact on the laser-induced damage threshold (LIDT) of treated sample surfaces. In order to find out the effects of these factors, we utilized the Taguchi method to determine the etching conditions that are helpful in raising the LIDT. Our results show that the most influential factors are concentration of etchants and the material etched away from the viewpoint of damage performance of fused silica optics. In addition, the additional acoustic power (∼0.6 W·cm-2) may not benefit the etching rate and damage performance of fused silica. Moreover, the post-cleaning procedure of etched samples is also important in damage performances of fused silica optics. Different post-cleaning procedures were, thus, experiments on samples treated under the same etching conditions. It is found that the "spraying + rinsing + spraying" cleaning process is favorable to the removal of etching-induced deposits. Residuals on the etched surface are harmful to surface roughness and optical transmission as well as laser damage performance.

[Effects of Chlorpyrifos on Dopaminergic Neuronal Viability with Activation of Microglia].

Excessive microglial activation and subsequent neuroinflammation lead to neuronal cell death,which are involved in the pathogenesis and progression of several neurodegenerative diseases such as Parkinson's disease.The objective of this study was to determine the involvement of chlorpyrifos(CPF)in the activation of microglia and production of inflammatory factors in response to CPF stimulation and the influence on the viability of dopaminergic(DA)neurons.We detected the change of BV-2cells morphology and expression of inducible nitric oxide(iNOS),cyclooxygenase-2(COX-2)mRNA and protein level upon CPF stimulation(0,1,3,6,12,24h)in BV-2(mouse brain microglia)cells by reverse transcription polymerase chain reaction(RT-PCR)or Western blot.We randomly assigned BV-2cells into CPF,menstruum dimethysulfoxide(DMSO)and normal saline(NS)groups.We stimulated The BV-2cells in the CPF group with CPF,and we stimulated the two control groups with DMSO or NS for 12 hours,respectively.We then collected the used culture media from the culture dishes and centrifuged it to remove the detached cells.Then,we used the supernatants as microglial conditioned media.We treated SH-SY5 Yneurons with various groups of microglial conditioned media for 24 hours.We observed the effect of conditioned media collected from BV-2cell on the viability of dopaminergic cell lines SH-SY5 Yusing MTT assay.We found that inflammatory factors iNOS,COX-2mRNA and protein levels were up-regulated upon CPF stimulation.Conditioned media from BV-2upon CPF stimulation is toxic to SH-SY5 Y.It might be concluded that the exposure to CPF may induce dopaminergic neuronal damage by the activation of inflammatory response,and a mechanism may be involved in Parkinson's disease pathogenesis.

Extrapontine myelinolysis associated with pituitrin: case report and literature review.

BACKGROUND: Hyponatremia is the most common electrolyte abnormality encountered in hospitalized patients, resulting from a varied spectrum of conditions. Both the primary disturbance and its correction can result in life-threatening neurological consequences. Extrapontine myelinolysis is one such complication that is associated with the rapid correction of hyponatremia. Here we describe a patient who developed extrapontine myelinolysis unexpectedly after the correction of hyponatremia, which involved the drug pituitrin. CASE PRESENTATION: A 24-year-old Chinese woman was transferred to our neurology department with the symptoms of dysarthria and quadriparesis developing one day after the correction of hyponatremia (from 118 mmol/L to 140 mmol/L), which followed with a continuous intravenous drip of pituitrin used to control hemoptysis in the emergency room. During the course, she developed involuntary movement. Magnetic resonance imaging changes were consistent with extrapontine myelinolysis. CONCLUSION: This present case describes the mechanism of profound hyponatremia involving pituitrin, and the subsequent development of extrapontine myelinolysis. Physicians may approach effective clinical management of patients through awareness of the adverse effect of pituitrin on serum sodium levels, and avoid rapid correction of hyponatremia in clinical practice.

Interleukin-16 polymorphism is associated with an increased risk of ischemic stroke.

Clinical and experimental data have demonstrated that inflammation plays fundamental roles in the pathogenesis of ischemic stroke. Interleukin-16 (IL-16) is identified as a proinflammatory cytokine that is a key element in the ischemic cascade after cerebral ischemia. We aimed to examine the relationship between the IL-16 polymorphisms and the risk of ischemic stroke in a Chinese population. A total of 198 patients with ischemic stroke and 236 controls were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing method. We found that the rs11556218TG genotype and G allele of IL-16 were associated with significantly increased risks of ischemic stroke (TG versus TT, adjusted OR = 1.88; 95% CI, 1.15-3.07; G versus T, adjusted OR = 1.54; 95% CI, 1.05-2.27, resp.). However, there were no significant differences in the genotype and allele frequencies of IL-16 rs4778889 T/C and rs4072111 C/T polymorphisms between the two groups, even after stratification analyses by age, gender, and the presence or absence of hypertension, diabetes mellitus, hypercholesterolemia, and hypertriglyceridemia. These findings indicate that the IL-16 polymorphism may be related to the etiology of ischemic stroke in the Chinese population.

Tentative investigation towards precision polishing of optical components with ultrasonically vibrating bound-abrasive pellets.

Ultrasonic vibration has been employed to improve the quality of machined surface in the grinding of brittle materials. In this report, we transplant the philosophy of ultrasonic vibration assisted grinding to chemo-mechanical bound-abrasive-pellet polishing in anticipation of the improvement in either surface roughness or material removal rate. The preliminary experimental results show that the ultrasonic vibration assisted chemo-mechanical pellet polishing can yield desired results that material removal rate can be significantly raised while surface roughness is not degraded. The experimental results also indicate different mechanisms between ultrasonic-vibration-assisted chemo-mechanical pellet polishing and conventional chemo-mechanical bound-abrasive polishing.

The Influence of Crystal Orientation on Subsurface Damage of Mono-Crystalline Silicon by Bound-Abrasive Grinding.

Subsurface damage (SSD) produced in a grinding process will affect the performance and operational duration of single-crystal silicon. In order to reduce the subsurface damage depth generated during the grinding process by adjusting the process parameters (added), experiments were designed to investigate the influence of machining factors on SSD. This included crystal orientation, diamond grit size in the grinding wheel, peripheral speed of the grinding wheel, and feeding with the intention to optimize the parameters affecting SSD. Compared with isotropic materials such as glass, we considered the impact of grinding along different crystal directions <100> and <110> on subsurface damage depth (added). The Magnetorheological Finishing (MRF) spot technique was used to detect the depth of SSD. The results showed that the depth of SSD in silicon increased with the size of diamond grit. SSD can be reduced by either increasing the peripheral speed of the grinding wheel or decreasing the feeding rate of the grinding wheel in the <100> crystal orientation, if the same size of diamond grit was employed. In addition, we proposed a modified model around surface roughness and subsurface crack depth, which considered plastic and brittle deformation mechanisms and material properties of different crystal orientations. When the surface roughness (RZ) exceeded the brittle-plastic transition's critical value RZC (RZC<100> > 1.5 µm, RZC<110> > 0.8 µm), cracks appeared on the subsurface. The experimental results were consistent with the predicted model, which could be used to predict the subsurface cracks by measuring the surface roughness. However, the model only gives the approximate range of subsurface defects, such as dislocations. The morphology and precise depth of plastic deformation subsurface defects, such as dislocations generated in the fine grinding stage, needed to be inspected by transmission electron microscopy (TEM), which were further studied.

3D Printing of Customized Aspheric Lenses for Imaging.

A simple and efficient process for fabricating customized aspheric lenses is reported, in which a stereolithographic 3D printer combined with the meniscus equilibrium post-curing technique is employed. Two kinds of UV-curable resins, DentaClear and HEMA, were used for printing aspheric lenses in our experiments. The printed DentaClear lens featured low surface profile deviation of ~74 µm and showed satisfactory optical imaging resolution of 50.80 lp/mm, i.e., 4.92 µm. The surface roughness of the printed lens with DentaClear was measured to be around 2 nm with AFM. The surface roughness was improved as a result of post-curing, which reduced the ripples on printed lens surfaces. In contrast, the printed HEMA lens exhibited a significant stair-stepping effect with a large surface profile deviation of ~150 µm. The ripples were somewhat apparent even if the printed HEMA lens surface was smoothed by means of post-curing. No sharp image can be obtained with the HEMA lens in the resolution testing. The composition of HEMA resin may be the reason for the relatively poor surface quality and optical properties.

High-Accuracy Surface Topography Manufacturing for Continuous Phase Plates Using an Atmospheric Pressure Plasma Jet.

The continuous phase plate (CPP) is the vital diffractive optical element involved in laser beam shaping and smoothing in high-power laser systems. The high gradients, small spatial periods, and complex features make it difficult to achieve high accuracy when manufacturing such systems. A high-accuracy and high-efficiency surface topography manufacturing method for CPP is presented in this paper. The atmospheric pressure plasma jet (APPJ) system is presented and the removal characteristics are studied to obtain the optimal processing parameters. An optimized iterative algorithm based on the dwell point matrix and a fast Fourier transform (FFT) is proposed to improve the accuracy and efficiency in the dwell time calculation process. A 120 mm × 120 mm CPP surface topography with a 1326.2 nm peak-to-valley (PV) value is fabricated with four iteration steps after approximately 1.6 h of plasma processing. The residual figure error between the prescribed surface topography and plasma-processed surface topography is 28.08 nm root mean square (RMS). The far-field distribution characteristic of the plasma-fabricated surface is analyzed, for which the energy radius deviation is 11 µm at 90% encircled energy. The experimental results demonstrates the potential of the APPJ approach for the manufacturing of complex surface topographies.